1. Field of the Invention
In internal combustion engines, throttle valves are used in the intake section and can be used to regulate the air volume that the internal combustion engine requires to combust the fuel. As a rule, the throttle valve includes a drive unit, the throttle valve supported on a shaft, and a throttle housing, which can be embodied as a cast metal part or as injection-molded plastic part. The throttle housing is often also provided with a separate housing cover, which can seal the housing to prevent outside air from being sucked into the valve.
2. Description of the Prior Art
The subject of DE 43 29 522 A1 is a throttle device that is built into the intake conduit of an internal combustion engine. The throttle device is comprised of a housing, a throttle valve control unit, a position detector, and a throttle valve supported on a throttle shaft; the throttle device is disposed between the clean air side air filter connection and the intake unit of the internal combustion engine. The air filter connection and/or the intake unit are made of a plastic; the individual elements of the throttle device are modularly designed and are attached to one another by means of plugged, screwed, or clamped connections. The throttle valve shaft is comprised of two parts. One shaft half of the throttle valve shaft can be provided with the module for the position sensor and the other shaft half can be provided with the module for the throttle valve actuating unit. The actuating unit, position sensor, throttle valve, and throttle valve shaft constitute a common component.
The subject of WO 95/2493 A1 is a molded article made of plastic, in particular produced by means of the injection molding process, and throttle valve housing with a wall whose inner wall surface borders a cavity. The wall contains an insert part that is covered by the plastic material, at least on the inner wall surface oriented toward the cavity. The insert part is inclined in relation to the normal plane in such a way that when a pivoting throttle valve, which is contained in the cavity and is used to control the output of an internal combustion engine, is disposed in its idle position, the insert part extends flush with it. The insert part can be made of metallic material, for example sheet metal.
DE 197 03 296 A1 has disclosed a method for sealing a throttle valve shaft, which supports a throttle valve, and a throttle valve connector. In a throttle valve connector for an internal combustion engine of a motor vehicle, a throttle valve shaft that passes through a recess in the throttle valve connector is sealed by a hardening sealant. The sealant prevents air from flowing through a manufacture-induced gap between the throttle valve shaft and the recesses.
EP 0 575 235 B1 relates to a rotating throttle mechanism for fuel injection systems of internal combustion engines. A shaft with cylindrical seats is provided, which has a segment for accommodating a throttle valve, which segment has a uniform, rotationally asymmetrical cross section that is greater than the cross section of the portion of the shaft to one side of the segment. The throttle valve has a central bore whose cross section corresponds to that of the segment. The shaft as a whole is comprised of plastic and is cast of one piece with a cam to be slung or wound around by a control cable that is disposed on the other side of the above-mentioned segment, the throttle valve itself being comprised of plastic, preferably a thermoplastic plastic. The segment of the throttle valve shaft is cylindrical, with parallel flattened zones. The throttle valve has a flattened hub with a central bore, which in cross section is the shape of a circle that is flattened parallel to the wings of the throttle valve.
DE 199 15 695 A1 relates to an intake element made of plastic and a method for producing it. A throttle body includes an inner main section made of plastic, a secondary section made of plastic, which is embodied as integral with an outer circumference of the main section, and an icing prevention tube, which is embedded in the secondary section. The cylindrically embodied main section with an essentially uniform wall thickness is produced in a first molding step in which shrinkage and distortion are suppressed in order to obtain the required roundness or circularity of an inner circumference surface of the main section. The secondary section is produced in a subsequent, second molding step so that an outside of the main section is covered in order to thus produce a throttle body. The temperature of one section of the mold oriented toward the inner circumference surface of the main section is set lower than the temperature of the other section of the mold. As a result, the inner circumference surface of the main section in which dimensional precision must be maintained is cooled earlier than the other section in order to effectively prevent shrinkage. If different types of plastic materials are used to mold the main section and the secondary section, this increases the degree of freedom in the selection of materials.